The serotype distribution of Streptococcus agalactiae (GBS) carriage isolates among pregnant women having risk factors for early-onset GBS disease: a comparative study with GBS causing invasive infections during the same period in Denmark.

BACKGROUND

We describe the serotype distribution of Streptococcus agalactiae (GBS) carriage isolates from women in labor and among GBS isolates causing invasive infections during the same period to see if the distribution of carriage serotypes reflects the GBS serotypes causing invasive diseases including early-onset disease (EOGBS).

METHODS

Data on invasive isolates from 2019 including serotype, erythromycin and clindamycin susceptibility was retrieved from the Danish national reference laboratory, Statens Serum Institut. Carriage isolates were collected from women with risk factors for EOGBS enrolled at delivery at the maternity ward at a Danish University Hospital, first half of 2019.

RESULTS

Among carriage isolates, the dominant serotype was IX (21 %) followed by serotype III (19 %). The resistance to erythromycin and clindamycin was 21 and 26 %, respectively. Among invasive GBS isolates, no case of EOGBS with serotype IX was detected but the distribution of serotypes were otherwise similar to the GBS carrier strains. The corresponding resistance to erythromycin and clindamycin was 23  and 15 %, respectively. Penicillin resistance was not detected among carriage nor invasive isolates.

CONCLUSIONS

The distribution of serotypes among carriage and invasive GBS reflects the assumption that EOGBS occur following transmission of GBS from mother to newborn, with the exception of serotype IX.